Permanently curled metal coated glass fibers



March 31, 1 4 H. B. WHITEHURST 3,126,608

PERMANENTLY CURLED METAL COATED GLASS FIBERS AND METHOD OF comm; THE SAME Filed April 5, 1961 2 Sheets-Sheet 2 INVENTOR.

HARRY B. WHITEHURST BY% 2 ATTORNEYS United States Patent 3,126,608 PERMANENTLY CURLED METAL COATED GLASS FIBERS AND METHOD OF COATENG THE SAME Harry B. Whitehurst, Tempe, Ariz, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware Filed Apr. 3, 1961, Ser. No. 100,4tl7 6 Claims. (til. 28--75) This invention relates to permanently curled glass fibers, the curl being produced by means of an asymmetrical coating of a material having a coefficient of expansion different from that of the glass. The coating is deposited permanently on the fiber and forms a part of the final product.

The present invention is based upon the discovery that a glass fiber can be permanently curled by applying a coating of a suitable material, e.g. of aluminum, on its periphery, which coating is thicker on one side of the fiber than on the opposite, and which coating contracts more during changed conditions than the fiber. A partial metal coating is desirable because it enhances the refiective properties of the fiber and achieves an unusual decorative effect. Apparently, this results because the partially metal coated fiber acts as a mirror to gather and reflect light passing through the fiber to a greater extent than occurs with a completely coated fiber. A fiber of this nature is discussed more fully in a copending application of Whitehurst et al., Serial No. 683,359. However, the coating of the present invention can extend completely around the fiber and need not be of metal but can be of any of many materials which, after being applied to the fiber, contract to a greater extent than the fiber. It is important that the amount of the coating material on the thickest side of the fiber be sufiicient in relation to the diameter of the fiber that it will curl as the material solidifies without deformation of the material, which otherwise will occur if the yield strength of the coating material is exceeded.

It is, therefore, a principal object of the invention to produce a permanently curled, coated fiber.

Other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a side view in elevation of apparatus for applying a coating to glass fibers during forming, which coating is thicker on one side of each of the fibers than on the opposite;

FIG. 2 is a front view in elevation of the apparatus shown in FIG. 1;

FIG. 3 is an enlarged view in vertical cross section taken along the line 3-3 of FIG. 2 of a coating applicater for forming a globule of coating material through which a fiber to be coated is guided;

FIG. 4 is an enlarged view in perspective of a part of the coating applicator of FIG. 3, showing an adjustable guide member for controlling the extent of immersion of the fiber in the globule;

FIG. 5 is a greatly enlarged, fragmentary side view of a portion of the applicator of FIGS. 3 and 4, showing a fiber partially immersed in and passing through the globule;

FIG. 6 is a greatly enlarged, fragmentary view in perspective of a glass fiber with a partial coating around the periphery thereof; and

FIG. 7 is a view similar to FIG. 6 but of a fiber having an eccentric coating around the entire periphery thereof.

A permanently curled, coated glass fiber according to the invention can be made in a number of suitable ways. One satisfactory apparatus for producing such a fiber is shown in FIGS. 1-5, which apparatus is a modification of that disclosed in Whitehurst and Otto United States Patent 2,772,518. Referring particularly to FIGS. 1 and 2, a bushing shown at 11 has a bushing tip 12 containing a plurality of fiber-forming orifices preferably arranged in only one or a few rows so that the fibers drawn therefrom will be in substantially the same vertical plane. Glass, generally in the form of marbles, but, if deisred, a batch or cullet is melted in the bushing 11, preferably by electrical heating. Continuous glass fibers 13, commonly referred to in the art as filaments, are attenuated from streams of the molten glass flowing from the orifices in the bushing tip 12 and are drawn past a coating applicator 14 by means of which a coating according to the invention is applied. The filaments are then led around a gathering shoe 15 which collects the filaments 13 into an untwisted strand 16. The strand is wound on to a package 17 on a forming tube 18 which is removably mounted on a collet 19 driven at a high rate of rotation by a motor 20.

As shown in FIG. 3, the coating applicator 14 has a well 21 lined with a suitable refractory 22 containing a coating material 23. The coating material 23 is heated by suitable means such as a coil 24 which can be electrically heated by resistance or by induction, to maintain the material 23 in a liquid condition. Gravity forces the molten material through a channel 25 which leads from the well 21 to an opening 26. The molten material 23 protrudes from the opening 26 to form a bead or globule 27 through part of which the filament 13 is drawn.

The entire applicator 14 (see FIG. 1) is mounted on a bracket 28 which is vertically adjustable on a threaded post 29. This enables the applicator 14 to be moved closer to or farther from the bushing tip 12 to vary the temperature of the filaments 13 at their points of contact with the globules 27.

The extent of immersion of the periphery of the fiber 13 in the globule 27 is affected by three principal factors. First is the amount of tension produced in the fibers 13 by rotation of the collet 19; increased tension tends to pull the fiber 13 into the globule 27. Second is the position of the applicator 14 (left or right in FIG. 1) with respect to a line between the bushing tip 12 and the gathering shoe 15; increased offset (to the left) increases immersion. Third is the extent to which the globule 27 protrudes from the opening 26 which depends on the size of the opening 26, the head of the material 23 in the well 21, and the surface tension and viscosity of the material 23.

However, as shown in detail in FIG. 4, a guide 30 also can be used to control the extent to which the filament 13 is immersed in the globule 27. The guide 30 is slidably mounted above the opening 26 in ways 31 and is rotatably connected to a threaded shank 32 which is turned to move the guide 30 in and out with respect to the globule 27. This enables the extent to which the periphery of each of the filaments 13 is coated to be controlled by the relative positions of the guide 30 and of the globule 27.

The degree of eccentricity and the thickness of the coating are affected by the extent of immersion of the fibers 13 in the globule 27, as discussed above. However, the thickness also depends on the temperature of the glass fiber at the applicator 14, the temperature of the coating material, the type of material, and the speed at which the filament is drawn through the globule. These factors can be varied to change the coating thickness and thereby to change the amount of curl obtained in a fiber.

The amount of coating material on the thicker-coated side of the fiber must be sufiicient to overcome the tend ency of the fiber to remain in a straight position and the opposing force of the coating material, if any, on the opposite side of the fiber, which tends to pull it in the opposite direction. The proper amount or thickness of the material depends upon the diameter of the fiber, the type of material used, and the amount of curl desired. If there is an insufficient amount of the material in relation to the fiber diameter, the fiber will simply remain straight as the material contracts and the material will stretch to correspond to the length of the fiber because the yield strength of the coating material is exceeded. On the other hand, if a very heavy coating is employed so that the coated fiber is, in effect, only a reinforcement for a rod or bar of the coating material, then again no curling will result. Although the thickness of the coating to produce a desired curly fiber can be calculated, in reality it is easier to find experimentally the proper thickness under given conditions.

In addition to having the proper thickness, the coating must be of a material which contracts at a different rate than the glass fiber. The coating, applied as a liquid, will begin to contract as it solidifies. At first, the liquid will simply slide along the surface of the fiber during the transformation period from liquid to solid, if its rate of contraction differs from that of the glass. However, the coating will finally reach an adhesion point or will become sufficiently viscous before reaching the solid state, that it will become fixed with respect to the fiber whereby the two must then move as a unit. After the adhesion point is reached, the coating material will continue to contract until it reaches the solid state, and, if above ambient temperature, will contract further until the ambient temperature is reached. The latter contraction is determined by the coefficient of expansion of the material. The fiber will also contract, if above ambient temperature when the adhesion point is reached, as it cools to the ambient temperature, as determined solely by its coefficient of expansion, there being no change of state therein. In order to achieve a curly fiber, it is necessary that the contraction of the coating material from the adhesion point to ambient temperature must be different from the contraction of the glass fiber from the adhesion point to ambient temperature. Otherwise, no curl will result.

Most materials will be applied to the fiber at an elevated temperature so that both the fiber and the material will cool considerably from the adhesion point to ambient temperature. However, some resinous materials can be employed at ambient or slightly higher temperatures, and will curl the fiber solely through their contraction or shrinkage from the adhesion point to their solid, or cured state.

One satisfactory, permanently curled strand, made of fibers coated according to the invention with the apparatus shown in FIGS. l-5, included fibers having diameters of about 0.00040 with an aluminum coating having a maximum thickness of 0.00005". Other effective, permanently curled strands have been made with coatings of 99% zinc and 1% tin, zinc and lead, and tin and bismuth. However, the coating according to the invention need not be limited to these materials because any material is satisfactory if it contracts as it solidifies at a different rate than the glass, and also is of a sufficient quantity and strength to prevent deformation during contraction.

Where a metal coating on a fiber is desired a metallic oxide can be applied and then reduced in a suitable reducing atmosphere such as hydrogen or methane and thus be converted from a ceramic to a metallic nature. This can be accomplished, for example, by a gas flotation technique in which the fibers with the metallic oxide coating are placed in a tower and suspended by reducing gases maintained at an elevated temperature.

FIG. 6 is an enlarged view of the filament 13 with a metal coating 33 applied by the apparatus shown in FIGS. 1-5. The coating 33 extends around only a portion of the periphery of the fiber when it is drawn across the surface of the globule without being completely immersed therein.

In FIG. 7, the filament 12 is shown with a coating 34 extending completely around the periphery but in an eccentric manner so that it is considerably thicker on one side than on the other. This is accomplished by pulling the filament through the globule 27 so that the filament is barely completely immersed in the globule, being just below the surface thereof. In this case, the portion of the filament closer to the orifice 26 receives a thicker coating because it is in contact with the molten metal for a longer period of time than is the opposite side which is immersed and in contact with the metal only at the very peak of the globule 27.

The strand 16 made with the apparatus of FIGS. l-4 will theoretically have all of the filaments 13 disposed with the thicker portions on corresponding sides thereof. Actually, however, some of the filaments 13 will twist between the applicator 14- and the package 17 so that their thicker portions will be on the opposite side or in other positions. Nevertheless, there will be a predominance of the filaments with the thicker portions of their coatings lying in a common direction so that curl will result. However, the curl will not be as pronounced as that of a single filament. Of course, the strand is straight when held under tension on the package 17 but assumes a curl when removed.

Other materials than those heretofore described which may be used to make curly fibers according to the invention include, by way of illustration and not limitation, silver, gold, copper, cadmium, antimony, 36% nickel-steel (Invar), porcelain, and combinations of fused quartz and glass.

The invention basically comprises a glass fiber of relatively uniform cross section with a coating extending over the length thereof which is thicker on one side of the fiber than on the opposite side, the material contracting from its adhesion point to ambient temperature at a different rate than the glass and the difference in thickness of the material on opposite sides of the fiber being sufficient to cause the fiber to curl permanently.

Various modifications and uses will be apparent from the above description and the accompanying drawings, and it is to be understood that such can be employed without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

l. A permanently curled, coated fiber comprising a glass fiber of uniform cross section throughout its length, a coating on said fiber which is thicker on one side thereof than on the opposite, the difference in thickness being sufficiently large in relation to the diameter of the fiber that the thicker portion of the coating material is substantially undeformed in its solid state at ambient temperature, and the coating material being contracted sufficiently more than the glass to cause the fiber to curl permanently toward the side on which the material is the thicker.

2. The method of producing a curly, permanently coated fiber which comprises applying a coating material in liquid form over the length of a glass fiber and to its periphery in a non-uniform manner so that the coating is thicker on one side than on the opposite, the thickness being suflicient to prevent deformation of said material during transformation thereof from its state at its point of adhesion to a solid state at ambient temperature, said material contracting more than the glass from the state of the material at its point of adhesion to a solid state at ambient temperature, and subsequently transforming the material from its state at its point of adhesion to a solid state at room temperature, whereby said material contracts more than said fiber and causes the fiber to curl in the direction in which the material is thicker.

3. A permanently curled, metal coated fiber comprising a glass fiber of uniform cross section throughout its length, a metal coating on said fiber which is thicker on one side thereof than on the opposite, the difference in thickness being sufficient that the thicker portion thereof is substantially undeformed in its solid state at ambient temperature, said metal having a coefiicient of expansion difierent from that of the glass to cause the fiber to curl permanently in a plane lengthwise of the fiber and extending through its axis and the thickest portion of the coating.

4. A permanently curled, coated fiber comprising a glass fiber of uniform cross section throughout its length, a coating along substantially the entire length of said fiber which is thicker on one side thereof than on the opposite, the difference in thickness of said coating being sufiiciently large in relation to the diameter of the fiber that the thicker portion of the coating material is substantially undeformed in its solid state at ambient temperature.

5. A permanently curled, coated fiber comprising a glass fiber of uniform cross section throughout its length, a coating of a solid material on said fiber which is thicker on one side thereof than on the opposite side, said material being contracted from its point of adhesion to a solid state at ambient temperature a different amount than the glass during cooling from the temperature at which the coating is applied to room temperature, the difference in thickness of said material being suificient in relation to the diameter of the fiber that the thicker portion of said coating is substantially undeformed in its solid state at ambient temperature.

"6. A permanently curled, coated strand comprising a multiplicity of glass fibers of uniform cross section throughout their lengths, a coating on each of said fibers which is thicker on one side thereof than on the opposite, the thicker portions of at least a majority of the fibers being on corresponding sides thereof, the difference in thickness of each of the coatings being sufficiently large in relation to the diameter of each of the fibers that the thicker portion of said coating is substantially undeformed in its solid state at ambient temperature, and the contraction of the coating material being greater than that of the glass to cause the fiber to permanently curl toward the side on which the material is thicker.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,945- Von Pazsiczky et a1 Oct. 19, 1943 2,428,046 Sisson et al Sept. 30, 1947 2,443,711 Sisson June 22, 1948 2,930,105 Budd Mar. 29, 1960 2,931,091 Breen Apr. 5, 1960 FOREIGN PATENTS 1,210,136 France Sept. 28, 1959 847,183 Great Britain Sept. 7, 1960 

2. THE METHOD OF PRODUCING A CURLY, PERMANENTLY COATED FIBER WHICH COMPRISES APPLYING A COATING MATERIAL IN LIQUID FORM OVER THE LENGTH OF A GLASS FIBER AND TO ITS PERIPHERY IN A NON-UNIFORM MANNER SO THAT THE COATING IS THICKER ON ONE SIDE THAN ON THE OPPOSITE, THE THICKNESS BEING SUFFICIENT TO PREVENT DEFORMATION OF SAID MATERIAL DURING TRANSFORMATION THEREOF FROM ITS STATE AT ITS POINT OF ADHESION TO A SOLID STATE AT AMBIENT TEMPERATURE, SAID MATERIAL CONTRACTING MORE THAN THE GLASS FROM THE STATE OF THE MATERIAL AT ITS POINT OF ADHESION TO A SOLID STATE AT AMBIENT TEMPERATURE, AND SUBSEQUENTLY TRANSFORMING THE MATERIAL FROM ITS STATE AT ITS POINT OF ADHESION TO A SOLID STATE AT ROOM TEMPERATURE, WHEREBY SAID MATERIAL CONTRACTS MORE THAN SAID FIBER AND CAUSES THE FIBER TO CURL IN THE DIRECTION IN WHICH THE MATERIAL IS THICKER. 